Dust seals for ball joints



May 27, 1958 M. A. MosKovlTz. 2,836,442

Dus'r SEALS Foa BALL JolNTs Filed July 19. 1955 5 Sheets-Sheet 1 FIGLI.

K l [ill j 577 :4.,: tenis-LLM E Y a l ai Ku-. ff I fJ/S C 10 AINVENTOR. MILTON A. Mosuovl 'r z A TToR/VEY May 27, 1958 M. A. MosKovlTz2,836,442

DUST SEALS Foa BALL. JOINTs Filed July 19. 1955 3 Sheets-Sheet 2 5INVENToR. F+x MlLToN A. MosKovlTz ww WW ATTORNEY May 27, 1958 M. A.MosKovlTz 2,836,442

DUST SEALS FOR BALL JOINTs 3 Sheets-Sheet 5 Filed July 19. 1955INVENToR. MlLro N A. MosKovl-rz BY y nite

This invention relates to ball joints generally of the kind used inmotor vehicle construction, but more especially to dust seals associatedwith such joints.

The invention has among its general objects the preduction of such sealsthat will be simple in design and construction, will perform theirintended functions ea ciently throughout the full range of movement ofthe joint parts, and which will be otherwise safe, satisfactory andefficient for use wherever found applicable.

One of the principal objects of my invention is to so construct such adust seal that there is full coverage ot the joint opening throughoutthe full amplitude of swing or tilt of the stud element of the jointstructure, and to obtain this coverage without impairing the strength ofsaid stud through any reduction of its eiective diameter that has beendetermined necessary for safety and strength of such stud.

Another object of the invention is to so construct such a seal of aminimum number of component sections that will insure adequate jointopening coverage even where more than a single dust seal element isrequired to accommodate a relatively wide angle of stud swing.

An added object of my invention is to provide stop arrangements for theseal elements of such a joint structure, so that over-travel of the sealelements sun'icient to uncover the joint opening, is prevented.

A further object of the invention is to design such a seal by precisemathematical computation from predetermined known factors such as thestud diameter, radii of the inner and outer bearing surfaces of thejoint housing and maximum angle of stud swing, and from theseascertaining the sizes of the other elements cooperating with said studand housing, as for example the minimum included or subtended angles ofcoverage by the dust seal elements.

Yet another object of my invention is to so construct such a jointwherein the inner seal element that is superimposed on the sockethousing is restricted for swing in substantially only a single plane.

A still further object of the invention is to have in such a jointconstruction, seal elements that are of dimensions that have beenmathematically computed in advance of their construction, and withreference to a horizontal plane passed through the common center ofcurvature of the socket member bearing surfaces and common center ofswing of the stud and seal elements so as to obtain maximum sealcoverage of the joint housing opening with or without overlap of saidopening by said seal elements, and also to ascertain the placement ofthe stop means, with reference to said horizontal plane, for halting theswing of said seal.

Referring to the drawings, wherein like reference characters representlike or corresponding parts throughout the views,

Figure l is a fragmentary vertical cross-sectional view through thejoint as mounted in position on a motor vehicle, showing the stud at themid-point of its swing amplitude;

faice Figure 2 is a similar view, showing the stud at one of its endlimits of swing;

Figure 3 is another similar View, showing the stud at one limit ofswing, with a modified form of stop means,

and with some of the internal parts of the joint omitted;

Figure 4 and Figure 5 show further modications of seal devices and thestop means associated therewith, and wherein the seals have an overlapbeyond the socket opening at the ends of stud swing;

Figure 6 is a perspective fragmentary view, showing a joint wherein theswing of the inner seal element is restricted to substantially a singleplane;

Figure 7 is a plan view of the same, as viewed from beneath; and

Figure 8 is an elevational view of the parts shown in Fig. 6.

Referring more especially to the drawings, wherein l have illustratedpreferred embodiments of my invention, there is shown a ball jointstructure of the type adapted to be in motor vehicle construction, asfor example, as a movable interconnection between the control arms andthe steerable wheels of the vehicle.

Although the use of ball joint suspensions is constantly increasing, ithas become increasingly diicult to so design such joints that they willeffectively seal out water, dirt or other foreign matter, the dicultyarising principally on account of the wide amplitude of stud swing thatis required to accommodate the proper movement of the parts `of such ajoint.

lt must also be remembered that in order to properly allow for thejounce and the rebound action of the vehicle parts to which the joint isattached, it is necessary that the stud swing be through a rather largeamplitude, and in this instance is shown as Iof about 64.

One of the ways of securing sufficient seal coverage for the opening ofthe socket, for a joint wherein the stud has such a wide angle of swing,was' to neck down or diametrally reduce the stud section at that portionof its length that was in the path of the bounding wall or" the socketopening through which the stud projected, and sometimes use a one-piecedust boot or seal to keep the socket opening covered.

However, it is obvious that any such reduction in the effectiveYdiameter of the stud shank, once the size of stud section has beendecided on for proper and safe strength, would proportionately decreasesuch strength and hence render use of such a weakened stud dangerous.Also, such a necking makes it uneconomical to manufacture such a shapeof stud in comparison with making such studs without such a cut-out andwhich can be made in the usual and well-known cold-heading process.

In the drawings, 1 indicates one of the control arms of the vehicle, and2 a part of the steering knuckle that is spaced therefrom, these partsadapted to be movably interconnected through a ball-joint structure thatincludes a housing or socket member 3 carried by said arm and which isclosed at one end (at the top as herein shown), by a cap 4, said socketmember having its interior hollowed or chambered and provided toward thelower end with preferably concentric segmentally spherical internal andexternal bearing surfaces 6 and 7, respectively, there being an opening5. through said lower end.

A stud is mounted within said housing chamber, so as to be freelytiltable and rotatable therein, having a radially enlarged head 9 andwith its shank 10 projecting outwardly through and beyond said opening5, for detachable interconnection to a portion of the knuckle element 2.

Intermediate said stud and the inner concave bearing surface of thesocket there is e bushing 11, that enclrcles said stud shank and isactuated by the stud, this bushing formed with an exterior convexsurfacev that is complemental to the inner concave bearing surface ofthe socket so as to be free torotate and Vtilt and slidably, engage thelatter during movement' of the stud.V

Resiliently yieldable means, asfor instance thefcoil spring 12 pressesapressure element `13 Constantly against the headofV said studto'maintainthe parts in their desired relationship. Y Y 1 The openingthroughl the lower end of the housing or socket is of such a size andshape as to permit 'of 'a predetermined and generallylarge degree oramplitude YofY stud tilt, and in this instance said amplitude is shownlas being of about 64, and the stud shank being adapted to substantiallyabut the bounding'wall of the socket vopen'-Y ing at the ends of swing.

ln order to prevent entry of water, dirt'fand other foreign matter intothe housing opening, I have provided a dust seal means of a minimumVnumberrof sections or components, that will effectively. maintain saidopening Said inner sealfis substantially cup or dome-shaped andpreferably segmentally spherical on its inner and outer concentricVsurfaces 16? and `17 respectively, with yits centers of curvature beingcommon to those ofY thev spherical surfaces -6'and V7, so that theslidably engaging faces of the inner seal and the socket'will have arelatively good tit, and vmaintain the socket opening covered, ashereinafter set forth.

This'inner'seal has an opening 18 centrally therethrough-,of a smallersize than the Vsocket opening, .and it is to be noted from inspection ofFig. 2that when the seal Vhas been actuated to one end of its swing bythe stud, there Vis no overlapping engagement-of the stud opening by the'other Vend of the seal. ln other words, the 'sizes ofthe Yparts aresuch that the seal will just cover thefsocket opening without overlap,at the' end limits of seal swing. Y

The outer seal is bored centrally to snugly` receive the stud shanktherethrough and has its inner face substantially concaveand with therim thereof in 'slidableengagement with Ithe `convex exterior surface oftheVY inner seal.

It is-'obvious that vas `the stud swings or tilts in'either direction,vsay tothe right as shown in Fig. 2,v from its mid-point position, theouter sealV always swing in unison therewith, while the vmovement of theinner seal lags relatively tothe commencement of outer'seal swing. How-V1=.ve,r,'as,soon'as the stud `has movedV toY approximately engagethcadjacent edge' of the inner seal opening, 'the seals then continuemovement together, in thesane advancing direction, until the stud shanksubstantially abuts the'V radially `innermost edge of the socketopening. In Figs. 1 3 there is'no overlap provided of the bounding edgeof the inner seal Yrelative to the socket opening at the Alimits ofswing; i Y l To prevent any possibility of the inner seal being moved(as it advances) suiciently to .have any portion uncovering `the socketopening, I have provided stop means that will positively stop furtherswing of the inner seal ,beyond its predetermined amplitude of swing,

these means-being operative at the ends of stud swing and interactingbetween said inner seal and some convenient relatively-'fixed part, asfor Yinstance: associated lwith the housing or the eontrol'arml Vfin'rligs l and 2, these stop 'means are in `the -forrn or" Va dared'portion` Ztl extending 'radially outwardly at an angle from the top edgeor rim of the spherical portion'fof the inner seal, said angle of flareC being 90 minus the angle of seal swing, this flared portion cominginto abutment with the housing exterior surface thatis above the heightof the horizontal plane that may be passed through the center ofcurvature of said convex surface of the socket.

V in Figure 3, these stop means are ing a shoulder 21 on the housing, inthe path of travel oi the inner seal, this shoulder lying in the sameplane as that passed through the center *of curvature, horizontally, otthe exterior convex surface of the socket member.

Here, swing movement of the innersealis limited when the advancing edgeof the latter abuis said shoulder, thus insuring that there is noover-travel of the seal with consequent uncovering of 'the` socketopening.

some cases, it is preferred that there be some overlap by the seal, toVcover the socket opening by a predeterming amount at the en ds of swing,and Vas indicated in l Figs. 4 and 5. This may be accomplished withoutchange o f swing amplitude, in several ways, two of which are aboutto'be described in more detaih inthe modication shown in Fig. 4, theinner seal is Y of the kind shownin Fig. '3, in that it does not haveits rim dared, but it Lis made deeperfby Van amount thatiis equal'totwice the predetermined overlap, and there is -l a shoulder 22associated with 'the control `arm there i Y shown, and in addition theexterior of thesocket has been Yout back-'or made substantially fiat sothat the socket element is reduced in cross section thereat, so that atthe end limitsrof swing, Vthe rimof said inner seal engages shoulder toprevent any` further advance 'in the' direction in which 'it is beingactuated;

in Fig.. 5, the 4stop'rneans is made by an auxiliary ange or shoulder 23carried by the control arm, the end limit of inner seal swing inrthiscase lbeing Yat a point that lies approximately in the horizontal planeypassed through the center of curvature of theconvex surfaceY of thesocket member. This subtended angle ofl maximum swing of the innersealis decreased'b'y one-half of the amount of desired overlap. 1Q

It is sometimes desiredjto restrict the swing offthe stud tosubstantially a single plane relative to the socketV member, and asindicated in Figs. 6-)8 inclusive wherein certain of theelements havebeen omitted for the sake of clarity.

The Vhousing or socket member is again provided with anexterior'segmentally spherical surface, withan Yopening through theVbottom of the socket. However, in vthis instance, the-opening 25 ismade elongated and of a width approximately equal-toY that of the shankvportion adjacent thereto, so that it is obvious that the swing of the Ystud is restricted to lengthwise of the opening.

The inner seal element is substantially as those previously described,having no iiared upper edge however, so that its Vrim rides on orslidably engages the convex exterior surface ofthe socket member, Vthemidpoint fof seal swing being'indicated in full lines inlFig. 8, whileits position'at one end of swing is indicated in dotted lines therein,

the center of seal swing being in the same' plane asj4 that passedhorizontally through the center of curvature of the 'said socketsurface.

In order to confine the swing of the inner seal element to thatsubstantially in a single plane, there is a shoulder 24 formedexteriorly of saidsocket member, said shoulder having 'its topmostportions at about the same plane as that passed horizontally throughYthe common center of uswing of the Ainner seal and of the convexityV ofthe socket member, whilethe lowermost pointsV of said shoulder is atabout the height of the rim of the inner seal when the latter is atv itscenter of swing (see.Fig.8).

It is apparent that ina device of such` construction, the inner vseal is`confinedl to swing in substantially a'single `plane, `the low points,of the shoulder 24 preventing .tilt ofthe seal upwardly in any directionexcept 'that lengthwise ofthe ysocket opening. At either end of. swing,the. advanced rim of the seal will abut the upper Vlimit of formed byprovidasses-te the shoulder to limit further movement in a givendircction.

lt is preferred that the various proportions and dimensions of sealparts be ascertained with certainty in advance of construction so as toinsure maximum coverage for each seal part, after first deciding on thediameter or stud required for strenoth, its amplitude of swing,curvature of the socket surfaces, and if overlap is desired, the amountof such overlap.

From these known factors it is possible to ascertain and calculate byformula, the minimum included or subtended angles of the dust seals andof other dimensions of these seals, as follows:

The known factors and the reference characters therefore, and asindicated in the drawings, are:

r=radius of stud shank at that portion that will engage the boundingedge of the socket opening C=ang1e of are of the rim of inner sealR==radius of curvature of the convex bearing surface of socket E=anglesubtended between stud axis at end of swing and adjacent bounding edgeof socket opening Szsubtended angle of stud swing to either side frommidpoint X=subtended angle of seal overlap desired at end of swing=actual distance of clearance between edge of inner seal at itsmid-point of swing and iixed abutment It is assumed that all centerlines are at 90 through the points of swing; that the stud swing cannotgo past the horizontal plane through the center of curvature of thehousing surfaces that are spherical; that all diameters are stated interms of degrees; and that there is a symmetrical condition of movementabout the Vertical center line or" the socket.

C=90angle of seal swing By construction, it is seen that the anglesubtended between the horizontal plane through the center of curvatureand the bounding edge of the socket wall opening at one limit of swing,and which is indicated as the angle A may be expressed as A=9D-(B+S).

The following are to be ascertained, in degrees:

l. Minimum angle subtended by the inside diameter of inner seal suicientto just cover the socket opening at swing limits;

Il. Minimum angle subtended by diameter of inner seal opening;

Iii. Maximum subtended angle of limits of inner seal swing to eitherside of mid-point;

EV. Minimum angle subtended across cocave end of outer seal that willengage the exterior surface of inner seal to either side of mid-point.

Where no overlap of the socket opening by the inner seal is desired, asin Figs. l and 2, the above-identified angles are determined as follows:

i. Minimum angie subtended by the inside diameter of inner sealsutiicient to just cover the socket opening at swing li- -its So, thatby substitution,

6 II. Minimum angle subtended by diameter ofinner seal opening B-I-S-r-ElV. Minimum angle subtended across concave end of outer seal that willengage the exterior'surface of inner seal to either side of mid-pointBut,

A+B+S= =90+E Also,

The angle of tiare of the inner seal rim=90angle of inner seal swing toeither side of the vertical center.

Where overlap of the seal relative to the socket opening at an end ofmaximum swing is desired, and which angular amount of overlap of theinner seal in indicated as X in the drawings, this overlap may besecured in either of two Ways, as follows:

First, as shown in Fig. 4, by deepening the inner seal element andwithout changing the angle of its maximum swing, allowing the seal totravel so that its advancing edge at the end of maximum swing is higherthan the horizontal plane passed through the center of curvature of theconvex surface of the socket, by said amount X In this example, therelationships are:

I. Minimum angle subtended by the inside diameter of inner sealsuiiicient to overlap the socket opening by said predetermined amount atswing limits il. Minimum angle subtended by diameter of inner sealopening But,

(same as for preceding determination for this angle, inasmuch there hasbeen no change in this dimension).

(same as for preceding determination for this angle; hence no change).

v herein one-half Inner seal opening IV. Minimum angle subtended acrossconcave end o Y outer seal that will engage exterior surface of innerseal (see proofof preceding computation for ,this angle, and to whichtwice the desired angle of seal overlap mut be added).

Second, and as shown in Fig. 5, by increasing theV size of the innerseal openingby the desired amount of angular overlap, keeping the limitstop positions at ends of maximum swing of inner seal at a point in thehorizontal plane through the centerrof curvature, said overlapindicatedras EX'S Y Y In this instance, the relationships are: Y

I. Minimum angle subtended by the inside diameter of inner seal that issutlicientto overlap the socket opening by the predetermined amount atthe limits of swing.

Ee-aot-z/iV A Y (see proof for same angle as previously given withoutIII. Maximum angle subtended by inner seal swing to either side ofmid-point Y I p S-l-B-(E-X) ,A-X 52* m T Inner seal wall depth remainingfor full swing after stud engagesagainst socket wall opening f IV.Minimum angle subtended across concave end of outer sea] that willengage exterior of inner seal to either side of mid-point Byconstruction (seev proof of preceding angle without .Y overlap, and towhich the desired overlap must now be added).

overlap, so that now, thev desired overlap must be added `for thedimension).

Yappertains, and by the claims here unto Having thusY descn'bedmyinvention, it is obvious that.

various immaterial modications may be made without departingV from thespirit ofthe invention; hencell do not wishto be understood as limitingmyself tothe exact form, arrangement,.construction and combination,except as limited'by the state ofthe art to which this'inventionappended."

I claim:

ll The combination with a joint ofthe typerthatkrincludes a hollow.socket member having an opening there-V through and with an angularlytiltable'stud therein, the j Vner seal member provided with an openingtherethrough larger than that through said outer seal member but whichis smaller than said opening through said socket member, and stop meansindependent of said stud and ixedly associated with said socket memberto limit advance of tilt in all directions of said inner'seal member. Y

2. The combination with a joint of the type that includes a socketmember with an opening therethrough and with an angularly tiltable studtherein and having a shank portion projecting outwardly through saidopening, said socket member having a segmentally spherical` convexexterior surface, of a dust'seal mounted on said socket member to coversaid opening at all degrees Vof stud tilt and comprising a pair ofnested inner and outer seal' members slidably interengageable and withthe pe-V ripheral portion of said inner seal member slidably engagingsaid convex surface of said socketV member during tilt of said sealmember, said outer seal member having an openingto receive said studshank andV said inner seal member having an'opening therethroughlargeithan that through said outer seal member, and stop'means independent ofsaid stud and operable at the end of stud tilt to halt further advanceof said inner seal member.

3. A device as set forth-in claim l, but which is further modiiied inthat said'stop means are between said housing member and inner sealmember and operable so that the leading portion of said inner sealmember may advance to a point that is above the height of the horizontalplane passed through the center of curvature o said convex surface ofthe socket member.

4. A device as set forth in claim l, but which is further modiliedinfthatsaid stop means includes an ele-V ment xedly associated with andexterior ofsaid socket member and engageable with said inner seal.

`5. VA device as set forth inclaim l, butwhichY is fur- Yther modifiedin that said stop means includes a peripheral rim portion of said innerseal member and which .Y is adapted to engagea fixed part associatedwith and exterior Vof said'socket member.

6. `A, device as set forthV in claim 2, but further moditied in thatsaid socket member opening is elongatedpand said inner seal member isrestricted to tilt in substantially f only aV single plane.

References Cited in the le of this patent I UNITED STATES PATENTS Y2,206,972 Niles Iulyv 9, 1940 2,486,246 Beeke Oct. 25, 1949 2,686,070Booth Aug. 10, 1954

